Condition responsive switch



Aug. 29, 1939. c. G. KRONMILLER E1' Al. y 2,171,272

l CONDITION RESPONSIVE SWITCH Filed Dec. 21, 1935 3 Sheets-Sheet 1 afZ -ffowragfjyalofae 32M M /6/ www Aug. 29, 1939. c. G. KRONMILLER ET AL 2,171,272

l CONDITION RESPONSIVE SWITCH Filed Dec. 21, 1935 3 Sheets-Sheet 2 Sme/nio@ CafZ G. Kforzfmz'ller lrfzef'lif Maloine Aug. 29, 1939. c. G. KRoNMlLLl-:R E1- AL 2,171,272

I ONDITION RESPONSIVE SWITCH Filed Dec. 21, 1935 l 3 Sheelzs-Sheerl 3 Painted Aug. 29,1939

f UNITED STATES -PATENT OFFICE y CONDITION RESPONSIVE SWITCH Carl G. Kronmiller and Homer E. Malone, Minneapolis, Minn., assignors to Minneapolis- Honeywell Regulator Company, Minneapolis, Minn., a corporation oI.' Delaware Application December 21, v1935, Serial No. 55,603

'29 Claims.

sible to make all desirable and necessary adjustments without any danger of distortion of the condition responsive element..

A further object of the invention is to provide an adjusting means for a condition responsive switch wherein a single element functions to prevent undesired movement of the adjusting means, as a means for indicating the setting of the adjusting means, and as a stopto limit the movement of the adjusting means.

A further object of the present invention is to provide a new and novel means for mounting a condition responsive switch wherein the means for mounting the same serves alsov as a means for making electrical connections to the switch elements.

A further object of the invention is to provide a novel mounting means for a condition responsive switch wherein the switch base is resiliently secured to the supporting surface and wherein it is impossible to distort the base by excessive tight ening ofthe fastening means.

A further object of the invention is to provide in a switch having 4a plurality of 'pairs of contacts sequentially engaged withmeans for indicating the change in condition necessary between engagement of the respective pairs of contacts.

A further object of the invention is to provide in a thermostatic switch employing an associated heater, a new and novel means for mounting said heater wherein the mounting means serves as the electrical connecting means.

A further object of the present invention is to provide a cover for a condition responsive switch in which a condition indicating instrument is mounted in a manner toprotect the same against damage, and in which said mounting means permits the initial adjustment of said indicating device.

Other objects ci the invention will be apparent from the accompanying specification, claims and drawings, ci which:

Figure 1 is a iront elevational view oi the condition responsive switch',

Figure 2 is a side elevational view of the switch proper taken in the directionof arrow I of Figure 1 with the base shown in section along the line 2-2 of Figure 1,

Figure 3 is a rear elevational view of the switch,

-cam surface of an adjusting cam 2|.

(CL 20G-139) This invention relates to a condition responsive Figure 4 is a section along the line 4-4 of Figure 1,

Figure 5 is an elevational View of the switch contact structure with a section through the base. 4

along the line 5-5 of Figure 1,

Figure 6 is a detail view of the switch blade structure,

Figure 7 is a perspective view of the terminal wall plate by which the switch is mounted,

Figure 8 is a rear view of the terminal wall plate,

Figure 9 is a section along the line 9 9 of Figure 1,

Figure 10 is a sectional view o f the heater ele- 15 ment,

Figure 11 is a schematic view of a control circuit i embodying the switch,

Figures 12 and 13 are front and side elevational views of a portion of a modified form of the switch, Figure 14 is a detailed view of a contact employed in the modiiied form,

Figure 15 is a perspective view of the. switch yassembled within the cover,

Figure 16 is a side elevational view of the cover and switch assembly with portions broken away, -Figure 17 is a section taken along the line I`I-I`I of Figure 16. Figure 18 is a detail view of a member employed in mounting a condition indicating device within the cover, and

Figure 191s a section along the line I9--I9 oi Figure 17.

Referring to Figures '1 and 2 of the drawings, the switch is shown as comprising a bimetallic member II bent to form a U-shaped member whichis pivotally mounted on a base I2. `One leg of said bimetallic member is provided with a pair of contacts I4 and I5 which are best shown in Figure 5. These contacts are adapted to engage with stationary contacts I6 and I1. The other leg I8 of said bimetallic member terminates in a curved cam follower I9 which engages the hel'ilcl e means for pivotally mounting the bimetallic member i l on the base comprises a bracket member 22 rigidly secured to said base by screws 23 and 24, shown in Figures 3 and,l 9. The bracket 22 pivotally supports a lil-shaped member 25 which is secured to the lower leg I8 oi the bimetallic element by any suitable fastening means.

As willy be apparent from the drawings, the bimetallic member I I is mounted diagonally with respect to the base I2. This permits the use of a longer bimetallic element for the same lentils of base. There is an even more important advantage in this arrangement and that is that the bend of the U shapedbimetal member is placed at an angle such that it is'more exposed to the air entering the cover of the switch no matter whether the air is introduced vertically or horizontally to the switch. Since the bend of the 29. A set. screw is threaded within the interior of stud 26. When the set screw 39 is not screwed into the interior of the stud 26, the latter member is in loose-threaded engagement with-` the bushing 28 permitting the cam 2| to be rotated with respect to the scale 29. Upon the set screw being tightened the same expands the stud` with the result that the threaded engagement between stud 26 and bushing 28 is correspondingly tightened so that cam 2| can no longer be turned with respect to scale 29 and -any movement imparted to scale 29 will similarly be imparted to the cam 2|. As best shown in Figures 2 and 3, a friction washer 3| is provided with three yresilient tongues 32, which engage the under surface of the base land yieldably' urge the scale against a Washer 33 which is located between said scale and thebase member. Stops 36 are provided to prevent said friction Washer from turning. The friction Washer is further provided with an extension 35 which extends outwardly'and upwardly through a slot 36 in the base and a 'slot 3l in' the scale member 29 and terminates in a pointer'3m8 overlying the scale. As is clear from Figure l'this pointer not only serves to give an indication of the adjustment of the cam but also constitutes a stop for limiting the movement of the cam by abutting with the ends of slot 31. As is usual with devices of this character, the

scale is graduated in terms of degrees, althoughV it is to be understood that the invention is not limited to a temperature responsive switch and that'in the event that some other condition than temperature is tovbe measured, ythis scale will be graduatedaccordingly. The adjusting means has associated therewith a device for locking the same at any desired setting. This device, as-

shown most clearly in Figure 4, comprises a pair of clamping members 39 and dll which are slidably located within a recess in the base i 2 and are held against lateral movement in the direction of rotation of scale member 2Q by the wallsV of said recess. The members are adapted to bev clamped together against the scale member 29 by means of a screw 63 in threaded engagement with member 4D. After the thermostat has been set at the desired position it may Ybe locked byl tightening of. thescrew 63. Since the clamping members are urgedwith equal force against the 'opposite sides of the scale, the scale is not subjected to a force' tending to distort the same, as when 'a single' clamping member' is employed.

'A' pair of contact mounting brackets ti and 62 are secured to the base. |2 through screws 43 and M ,as shown in Figure 5. Bracket 4|, as best' shown'in Figure 1, isprovided with a forwardly extending arm i5 which is provided with a screwthreaded aperture t5 and is slotted at il to resiliently engagea contact screw 'dd in said aperture fis.Y The connection between contact screw.

te andthe arm as is suncienuy tight that the 7 screw can only be turned when 4an appreciable amount of pressure is applied to the same. In this manner there is an assurance that any acl-l justment that may be made will not be accidentally altered. Th'e bracket t2 is similarly prol vided with a forwardly extending armi corresponding to the arm d5 of bracket 59.7 This a` is similarly slotted and provided with-a serez-*Q threaded aperture into which a contact screvwtd" is threaded. As in connection with the previo y described contact and bracket structure, the engagement of the screw 5|] with the aperture of arm t9 is rather tight so as to prevent accidental disturbance of the adjustment of said screw. This contact andlarm structure diiiers from the previously described'onahowever, in 'thatthe contact screw is provided with a dial 5| adjacent the' head of the screw which is provided with nu` merals or other indicating media thereon. The arm Q9 is provided with a pointer 52 which cooperates with the indications on said dial to give an indication of the setting of screw 5i). Extend- 'ing between brackets ,4| and 42' is a bar 53 of insulating material. This bar is for the purpose `of limiting the outward movement of the bimetallic contact arm as will be presently described.

The bimetallic contact arm structure is best shown in Figure 6 and comprises a contact' carrying member 54 which is rigidly secured to the leg |3 of the bimetallc element. The contact carrying element 54 is provided with two for- -wardly extending legs 55 and 56. Leg 55 carries the contact |4 which is adapted to engage with contact i6. The leg 58 has attached thereto a resilient contact blade l5`| which carries the contact 5 adapted to engage with contact The leg 56 is bent upwardly and extends along the upper side of the contact blade 57 spaced a sufcient distance from the same to permit ilexure of the blade outwardly. y The end of the leg 56 is' bent around and terminates in a portion 53 vengaging the under side of contact blade 5l to limit inward movement thereof. The portion 5d ex.

. tending over and engagingthe contact blade'5l provides a means for adjusting the tension of the resilient blade. By bending the leg 66 in either direction, the tension oiJ the blade 57 can be changed as will be readily apparent. The contact carrying element 54 terminates in an inwardly extending hook 59 which engages the `'bar 53- to limit the outward movement of the legl i3 of the bimetallic element.

The means for mounting theswitch to a wallor other supporting surface is best shown in Figf/ such as rivets. Mounted on the plate E6 of insulating material are three terminal -members 6l, -58 and 69. Each of these members is provided with a pairof tongues 'i0 which extend through an aperture in the insulated plate 66 and arebent over to engage the wall side of the insulated. plate and secure the terminal member' thereto; as most clearly shown in Figure 8A. Each 75 45 dition responsive Switch takes the form o! a m 2,171,272 of these terminal members 61, 68 and 68 are fur-- ther provided with two ears, both of which have threaded apertures. In each case, a binding screw 1I is located in the threaded aperture of one of said ears and serves to permit the connection of an electrical conductor to said terminal. The aperture in the other ear i's adapted to receive a screw12 which is permanently secured to the switch member,v Asbest shown in Figures l and 2 these screws extend through resilient arms 13 which arms are adapted to engage the terminals 61, 6,8 and' 88 and secured theretov by engagement of screws 12 inthe apertures opposite those in which binding screws 1| are located. Mounting brackets 22, 4I and 42 are provided with ears 1.4, 18 and 16, respectively, as indicated in Figure l. Each of 'these ears is provided Awith an aperture of sumcient size for the insertion of a screw driver which aperture communicates with an aperture of slightly greater diameter in the base' and is located in .line with one of the screws 12 so as to permit .tightening of the same therethrough. While these apertures are of suiilcient size to permit the insertion oi a screw driver, they are not of as large a diameter as that oi, the heads of the screws 12 so that it is impossible for the screws 12 to pass therethrough. In this manner the screws 12 are permanently retained in assembled relation with the switch structure so that there is no danger of their being lost therefrom. It will further be noted that no matter how tightly the screws 12 are turned it is impossible to apply any stress to the base I2 and no matter how tightly these screws are tightened, the base I2 is yieldably mounted on the terminal plate 6I by reason of the yieldability of the members 13. In this way there is overcome the disadvantage of certain Prior art structures wherein the insulated base of the switch structure was directly connected to the wall plate and if the fasteningmeans were excessively tightened the base of the switch structure would be distorted, -disturbing the adjustment of the various settings.

It is desirable in certain cases where the conthermostatic switch to employ a heater in connection therewith to accelerate the action ofethek switch during a certain portion of the operating cycle.

In Figures 9 and 10 thereris shown a meansv providing for such a heater. The heater 96, as shown most clearly in Figure l0, comprises a slotted screw-threaded metallic head 91, a pin member 88, and a sleeve of insulating material which is secured to the head 91 and surrounds and engages the pin 88. Around this insulating member is wound a heater element 99 which has one end secured to a washer of conductive material in engagement with the end vof the pin 98 by any suitable means that will .enable a good electrical connection to be obtained, such as soldering. The other end of the heater element is similarly soldered to the head 81. The heater 88 is adapted to be located in a housing 18, which housing is interiorly threaded at its upper end to receive the threaded head 91 oi the heater. The housing is retained to the base i2 by means of a screw 24. The housing is provided at its lower end Witha slotted cylindrical extension 19 which is adapted to iit into a splined opening 88 in the base of bracket 22,50 as to be held nonrotatably therein. YThe screw 24 has interposed between its head and the .base of the housing 18 au insulating washer 82 and is threaded to the base and engages at its other end the resilient member 13 which, as explained previously, is electrically connected with terminal 61. The slotted head 91 of heater 96 is screwed down suiliciently within the housing 18 so that the end of the pin 98 engages the head of screw 24. In-this manner one end of the heating element 99, which is connected to this end of the pin, is electrically connect-e-:l through screw 24 and resilient member 13 with terminal 61. The other end of the heater element is electrically connected through the pin head 91, the housing 18, the base of bracket 22, and a jumper 8| with the bimetallic element. Ii for any reason it is desired not to employ a heating connection in the thermostat all that is necessary to do is to unscrew the heater unit 96, unscrew the screw 24, remove the housing 18 and the insulated washer 82 and replace screw 24, screwing it down until it enters the circular portion of the opening 8U'. tween terminal 61 and thel bimetallic element will then be made directly through element 13, screw 24 and the base of bracket 22 to the jumper 8|,

In Figure 11 there is shown a wiring diagram of a circuit employing the thermostatic switch of the present invention when using a heater. A step-down transformer 84 is used to supply low voltage current to the circuit. The transformer comprises a line voltage primary 85 and a low voltage secondaryv 86. One end of this secondary is 'connected to contact I1 and the other end thereof is connected to one terminalof a relay coil 88. This relay coil is associated with switch arm 89 and 98 which are adapted to engage with contacts 9| and 92, respectively, upon energization of said coil. Switch arm and contact 82 control the operation of the temperature varying means; thus this contact arm and contact may control the operation of an oil burner motor, a gasvalve or some similar device. Contact 9I is connected to the heater 96, which 'in turn isr connected to the bimetallic element II. tacts I5 and I1 are less widely spaced than contacts I4 and I6 so that upon a decrease in temperature contacts I5 and I1 are first brought into engagement. Bimetallic element yII is adapted to move in the direction of contacts I6 and I1 upon a fall in temperature. Upon such a fall in temperature taking place, contacts I5 and I1 are first brought into engagement. The engagement of these contacts, however, does not establlsh any circuit.` If the fall of temperature continues, contacts I4 and I6 will eventually be brought into engagement by reason of the fact that contact I5 is mounted on a yieldable arm 81 as shown and described in connection with Figure 6. Upon the engagement of contacts I4 and I8, the following energizing circuit is established: From secondary 86 through conductor 93, contacts I1 and I6, contacts I4 and I6, conductor 94, conductor 95, relay coil 88 and conductor IIS back to the secondary 86. The establishment oi this energizing circuit results inrelay coil 88 being energized and causing the engagement of contact arms 89 and 89 with contacts 9| and 92, respectively. The engagement of switch arm 90 with contact 92 completes the circuit of the temperature varying means. The engagement of contact arm 88 with contact 8l `establlshes a holding circuit for relay coil 88. This holding circuit is as follows: From secondary 8 6, through conductor 93,contacts I1 and I5, bimetallic element II, heater 86, conductor I41, contact 9| and switch arm 89, conductor 96,

The connection be,

Con-

95 and theother of these circuits being merely, `across the contact carrying portion of the thermostat.

8S. Thus, so long as both contacts I5 and ill and contacts le and i6 are in engagement there will-.be two parallel circuits through coil t8, one of these circuits including the, heating element Since the formerV circuit is`of much higher resistance because of the presence of the high resistance heating element very little current will ow throughthis circuit. As the temperature of the space arises due to the operation of the temperature varying means, the thermostat il will be gradually deflected in that direction tending to move contacts ,IB and i6 away from contacts l5 and |'l. After this action has continued for a short time contacts M and i6, which as previously mentioned are more widely spaced; will -be moved out of engagement, leaving contacts i5 and lll still in engagement. When this takes place the only circuit through relay coil 88' is through the' heater 9G so that a large current will ow through the heater. This will cause the heating element to raise the temperatureadjacent the thermostat with the result that in a comparatively short period of time, the ther-` v mostat lis denected sufficiently away from contacts |5 and that th-disengagement of contacts l5 and is eiected. It will be seen that the effect of the heater 96 is to accelerate the breaking of the contacts of the thermostatic switch after the temperature in the space has begun to rise by reason of the operation of the temperature varying means. By reason oi' the sequential engagement of contacts I5 andi? -and i4 and I6, a -chattering action is avoided in that very slight movement of thethermostat to th right will not put into operation the temperature varyingmeans, nor after both pairs oi' contacts are in engagement will a slight but temporary temperature rise suicient only to cause disengagement of contacts ll and i6 momentarily, cause the temperature varying means to be put out of operation.. However, when the rise in temperature is not merely a temporary one, but is indicative of gradually rising temperature by reason of the operation of the temperature f varying means the heater 96 functions to cause a more rapid disengagement of the thermostatic contacts so as to lessen the danger of the temperature rising above the optimum temperature.

1f such a means is not provided it is quite common for the temperature\to rise a number -of A,degrees above the desired temperature after the thermostat has put out of operation the temperature varying means, due to the ,time lagl between lthe production of the heatin'f'th iur-` Contact screw de is then adjusted so 'that upon turning the scale 2|l through the number of degrecs.' indicated on the dial 52, the bimetallic element will be;moved from a position in which only contacts l5 and il] are in engagement to a wardly extending arm lll of a bracket H2.

s relay coil te, conductor ||5 back to the secondary position wherein both pairs of ycontacts are in engagement. After this done, the adjustment ofthe cam 2i with respect 'to the scale 29 may be made by the means previously described so that the scale 2S indicates the temperature at which engagement oi' contacts i5 and il takes place.

en this is done, the scale 29 maybe turned -to any desired temperature setting and locked therein by the locking member-39. The thermo- .stat will thus be provided with means for both indicating the temperature at which the thermostat will operate and the temperature dierential required to effect such operation. Y

In Figures 12 and 13 there is shown a modiiied. form of a condition responsive switch. This formV ofthe switch differs structurally from the previously described one only in the arrangement of the contacts. Instead of the bimetallic ele: ment carrying a pair of contacts which sequentially engage stationary contacts, the bimetallic member carries a switch arm which is movable between two opposed'contacts. Referring to the gure, the .bimetallic element is' here designated by the reference numeral |00 and has attached thereto a switch arm |0I. This switch arm is 25 provided with two contact members |02 and |08 on opposite sides thereof, which contact members are adapted to engage with contacts |04 and |05, respectively. Contact ,|05 is rigidly and nonadjustably secured to a forwardly extending arm nally threaded bushing |09 which is most clearly shown in Figure 14. Bushing |09 is provided with a scale ||0 which is provided with numerals on the face thereof in a manner similar to dial 5| of the preferred species. Bushing |09 is 1o; catedwithin a screw-threaded aperture in a ior- The forwardly extending arm is slotted, as indicated in dotted lines in Figure 12, at H3. As in the previous species, the slotting of this arm is for the purpose of making the same resilient and causing the same to tightly engage the number |09. The

arm is provided with a pointed projection |.|l

which cooperates withv the scale ||0 to indicate the setting thereof. 'In initially adjusting the device the bushing |09 is rotated. in the arm by means of a slot in the head thereofuntil the value of the temperature differential desired .is indicated on the scale ||0 opposite the pointer lld. Screw |08 is then'turned within the bushing |09 until the Ispacing between contacts |04 and |05 is such that the temperature differential indicated on the scale ||0 is necessary to cause movement of switch arm |0 from engagement 'with contact |04 into engagement with contact |05. .When this isdone the setting of the scale llugis' an indication of the temperature Vdiio A fer'e'ntial at which the apparatus is set to operate.

In Figure 15 there is shown the condition 1re--v sponsive switch mounted'- within its cover. In the form shown, the condition responsive switch 'is a. thermostatic switch anda thermometer IIS is located within the cover ||1 back of an opens ing H8 therein so as to be visible from the iront of the cover. Adjacent the opening are gradu.' -Y

thereof through which thev scale 2@ projects so Y as to make the thermostatic switch readilyadations indicating degrees of temperature. i The cover V| li is provided with a. slot at the upper end justable without removing the cover. As shown in Figure 16, the cover is retained in position te Y upon the switch vby means of a screw |19 which extends through a slot |29 -in said cover and is v in-threaded engagement with the switch base |2.

I passage of air adjacent the switch. In the upper edge of the central portion of the casepa grilled opening is provided by striking out portions of the cover. These portions v|2| and |22 are utilized to retain the thermometer in place as indicated in Figures 1'1 and 19 and as will be pres- Y 'ently described. The thermometer ||6 is mount- 15 ure 18. This strip is'provided at its upper end ed upon a strip |23,4 shown most clearly in Figwith a transversely extending strip |24 whose ends |25 areturned inwardly. The lower end of the strip is enlarged as at '|26 and terminates in a slotted end portion |21 of relatively narrow width. 'I'he enlarged portion |26 of the strip is provided with an opening |29 therein and adjacent the upper end thereof there are two inwardly directed prongs |29. Thethermometer IIS, as is usual, vis provided with a bulb |30`at its lower end and atY its upper end is provided with a turned sealed tip |3|. through an opening |32 in strip |23 and is sealed thereto by sealing material |33. The bulb of the thermometer projects through the opening |29.

The stem portion of the thermometer extends between the tongues |29. As most clearly indicated in Figure 19A the opening ||8`in the cover ||1 is formed by striking inwardly a portion thereof leaving two inwardly extending strips I I and |35. 'Ihe thermometer stem is located between these two strips and is held in positionthereagainst. At its lower end the cover ||1 is provided with an upwardly extending strip |36` which strip 1s provided with a screw-threaded aperture adapted to receive a screw |31. Screw |31 serves as a means for securing the strip |23 with its associated thermometer lli-in position. As previously mentioned,` this strip is slotted so as to permit initial adjustment of the thermometer and strip in a vertical direction 'until the thermometer is in a proper position relative to the scale on the cover. When this adjustment is obtained the screw |31 is tightened to prevent any further vertical movement of strip |23 and sealing material |33 is employed tol prevent this adjustment being disturbed` t*The upper of strip |23 is retained in positiimby means of 'strips |2| which engage with thetransverse portion |24 of strip |23 and hold the same in position with the inwardly directed ends |25 abutting the inner surface of the cover ||1. As will be readily seen from the foregoing description, the thermometer,

1 lafter the initial adjustments have been made. is

permanently and securely held in position by a construction which is relatively simple. l Y

It will be seenthat a condition responsive switch has been providedin which provision is made for all desired adjustments through a simple, compact structure which is relatively free from damage byA careless installation, and in which all 'adjustments can be locked to prevent accidental" disturbance there'oL 'I'he invention l further provides a thermostatic switch employing a heatenin which the heater'element is of relatively simple construction employing the securing means` therefor both as mechanical securing` means and electricalconnecting means. At the same time, provision is made for very simply removing the heater and adapting the thermostat This tip |3| projectsV for operation of the same without any alterations thereof. Thereis further provided a mounting structure for a switchof this type wherein the switch is resiliently secured to the mounting structure yto prevent any damage to the base of the switch. 'Ihere is further provided a new and l novel switch cover structure in which the ther-- mometer is held within the cover where it is not 'so easily damaged by a relatively simple holding structure which employs elements whichy are struck out of the cover for other purposes.

While two specific embodiments of this invention have been described, it will be understood that these are for purposes of illustration only,

and that the invention is to be limited only by Y justing vcamlhaving a helical surface and rotat- Y ably mounted on said base with the axis of the helix extending perpendicularly to said base, said temperature responsive element comprisingv an elongated member engaging said cam surface and extending parallel to a. line tangent to the cam surface at the point of engagement of said elonggated member therewith and which elongated member is substantially perpendicular to a line intersecting the said axis and the cam surface at the point of engagement with said elongated member.

2. In a thermostatic switch, a base member, a temperature responsive element in the form of a flat strip of material bent at an intermediate point to form a U-shaped member, means mounting said temperature responsive element Ifor pivotal movement perpendicularly of said base, a xed contact secured to said base, a contact on one leg of said U-shaped temperature responsive element adapted to 'be engaged with said fixed contact upon said element beingfsubjected to a temperature of predetermined Value, and means V ing disposed parallel to a line tangential to said cam surface at the point of contact of said leg. therewith, and which is substantially perpendicular -to a line intersecting the -said axis and the cam surface at the point of engagement with the said leg. Y

3. In combination, a base, a switch mounted on said base, switch adjusting means comprising a rotatable cam member, a scale member rotatable about a common axis with said cam member and means for adjustablysecuring said scale member to said cam member for rotation therewith, an indicator iiexdly secured to said base and cooperating with said scale member t'o give an indication of the setting ofsaid adjusting means and to limit the range of movement of said means.

. 4. In combination, a base, a switchA mounted on said'base, yswitch adjusting means comprising a cam member rotatably mounted in said base, a scale member rotatably mounted in said base and having an arcuate slot therein, means for adjustablysecuring Vsaid scale member, to'said cam member for rotation therewith, an indicator ilxedly secured to said base and projecting through the arcuate slot in said scale member to cooperate therewith to give an indimtion of the setting of said adjusting means and to t rota= tion of said com and scale members by engagement with the ends of said slot.

5. In combination, a base, a switcgii mounted on said base, switch adjusting means compe' a cam member rotatably mounted on said base, a

scale member rotatably mounted on said base and A having an arcuate slot therein, means for adjustu ably securing said scale member to said cam member for rotation therewith, yieldable means for preventing unimpeded rotation of said cam.

member, said means comprising an elongated member projecting through the arcuate slot in said scale member to give an'indicationof the setting of said adjusting means and to limit rotation of said cam and scale members by engagement with the ends of said not.

6. In combination, a, base, a switch mounted on said base, switch adjusting means comprising a Y cam member rotatably mounted in said base, a

means for adjustably securing said scale member scale member rotatably mounted in said hase,

to said cam member for rotation therewith, an indicator xedly secured to said base and located adjacent to said scale member to give an indication of the setting of said adjusting means, and

clamping means to lock the cam and scale members in any desired-adjusted position.

'7. in combination, a mounting plate, means for securing the mounting plate to a supporting surface, connecting terminals on said plate adapted to engage the ends of electrical conductors, a base, a switch on saidbase, terminals on said base electrically connected lto said switch, spring ngers secured to the terminals on said base, and

indicating device, means for mounting said de` vice within said cover in a position such that-it is visible through the opening, said means ccm= prising an elongated member to which said indicating device is attached, and inturned portions' on said cover retaining said member and attached indicating device in position.

9. In a condition responsive mech a con.

dition responsive switch, a cover for said switch, said cover having an og therein, a condition indicating device, means for mounting said device within said cover in a position 'such that it is visibiethrough the opening, said means coro.- prising an elongated strip to 'which said indicating member is attached,` a plurality ci' inturned Atongue members strucis out ci said cover to provide an opening thereinl icr the adon ci air to the switch and engaging said strip to retain it and said indicating memner in position, at least one of said tongue mem-hers having means associated therewithv for rigidly said strip and attached condition indicating member in any desired position with respect to said opening.

10. in combination, a base, a thermal respon-4.

sive switch mounted on said bese, an electrical heater locatednear the switchend adoratori` to modify the action of :alsl switch a te on said base, means electrically'connectingone termina! oi said heater to an element oi said switch i and means for attaching said heater to said base,

' said attaching means serving to connect the other terl of said heater to said terminal on said base.

il. In combination, a base, a thermal responsive switch mounted on said base, an electrical heater located near the switch and adapted to modify the action of said switch, aterminal on said base, a housing for said heater, said housing electrically connecting one terminal of said heater to an element oV said switch and means .for attaching said housing to said.base, said attaching means serving -to connect the other terminal of said heater to said terminal on said base. j

12.1n combination, a base, a condition nra sive switch comprising two switch members and a condition responsive element for moving said members into and out of engagement, m ionv adjusting the value ofthe condition at weh engagement ci said contacts takes place comprising a disc rotatably mounted with respect to said base, locking means for said disc comprising two clamping members disposed on opposite sides of said disc, means for clamping said members against said disc, and means ,on said base to prevent displacement of said clamping members in the direction of rotation of said disc.

i3. in a thermostatic switch, a base member. a substantially U-shapcd thermostatic element, means mounting said thermostatic element for movement perpendicularly ci said base member, a xed contact secured to said oase member, a Contact operated by said U-shaped thermcstatlc element :for engaging said :diced contact upon said element being subjected to a temperature oi predetermined value, and means for moving said U-'shaped thermostatic element for adjusting the value of the temperature at which engagement taires piace, said means including a rotatable member mounted on said base member and hav- -ing a helical cam surface, the axis of rotation oi said member being perpendicular to said hase member, and' iriction means associated with said rotatable member for holding said member in its rotatably adjusted positions.

ii. In a thermostatic switch, a base member. a substantially lli-shaped thernicstatic eiefment,

means mounting said thermcstatic element for movement perpendiculariy ci said base member, 'a xed contact secured to said base member, a movable contact carried by one leg ci the ilshaped thermcstatic element and adapted to engage and disengagesaid fixed contact at predetei-ed temperature values'aecting said 'U- shaped thermostatic element, said thermcstatic element moving said movable contact toward and away from said oase member upon changes in temperature, and means operatively-asscci-- ated with the other leg or the lJ-shaped thermostatic element for moving said thermostatic element perpendicular-ly ci said base member for adjusting `the temperature values at which said contacts engage and disengage, said means in' v cluding a rotatable member' mounted on Said base member and having a `helical ycam surface,

, the axis ci' rotation ci said member being perpendicular to said hase memoer, an arcuate groove ln'said rotatable member, and e proies tion carried hy said lease member extending into said arcuate groove to limit rotation oi said rotatable member. f

15. In a thermostatic switch, a base member, a thermostatic element in thev form of a strip bent at an intermediate point to form a temperature responsive device having two substantially parallel legs, means mounting said temperature responsive device on said base member for movement about an axis parallel to said base member and with the legs arranged substantially parallel to said base member, one leg being more remote from the base member than the other, a fixed contact secured to the base member, a movable contact carried by the more remote leg of the temperature responsive device and movable to' ward and away from the fixed contact upon temperature changes affecting the thermostatic element, and means operatively associated with the less remote leg of the temperature responsive device for moving the temperature responsive device about an axis parallel to the base member whereby the temperature setting of the thermostatic switch is adjusted, said last-mentioned means including a rotatable member mounted on said base member and having a helical cam sur-` face, the axis of rotation of said member being perpendicular to said base membenand means I associated with said base member for limiting rotation of said rotatable member.,

16. In a thermostati switch for controlling an apparatus, a base member, a substantially U- shaped thermostatic element, means mounting the thermostatic element on said base member, a pair of iixed contacts secured to said base member and located on the same side of the thermostatic element, a pair of movable contacts carried by one leg of the U-shaped thermostatic element and adapted to engage and disengage said fixed contacts at predetermined temperature values affecting said U-shaped thermostatic element for closing and opening a circuit across said fixed contacts and turning on and off the apparatus, said thermostatic element moving said movable contacts toward and away from ,said base member upon changes in temperature, means for adjusting one of said fixed contacts for adjusting the temperature value at which said contacts engage. and disengage, and

means forindicating the adjustment of said adfinstable xed contact said means including a member with a plurality of markings thereon, a

member with a single marking thereon, the single marking cooperating with the plurality of markings for performing the indicating function and means for operating one of the members upon adjustment of said adjustable fixed contact.

17. In a condition responsive mechanism, a condition responsive controlling mechanism, a cover for said mechanism having an elongated opening therein, flanges Valong the edges of the opening inside of the cover, an elongated condition indicating device insaid cover engaging said flanges, anelongated strip `coextensive with the elongated indicating device for holding the `indicating device against said flanges, and means `i'or securing the extremities of. the elongated strip to the cover.

18. Iln a condition responsive mechanism, a condition responsive controlling mechanism, a cover for said mechanism 'having an elongated opening therein, flanges along the edges of the opening inside of the cover, an velongated condition indicating device in said iangs, an elongated strip coextensive withthe -longated indicating device, means for fastening said indicating device to said strip, and means for securing the extremities of the strip to said cover engaging said,

cover for holding the indicating device in a predetermined position against said'flanges.

19. In a condition responsive mechanism, a condition responsive controlling mechanism, a cover for said mechanism having an elongated opening therein, flanges along the edges of the opening inside of the cover, an elongated condition indicating device'in said cover engaging said flanges, an elongated strip coextensive with the elongated indicating device, means forv fastening said indicatingvdevice to said strip, and means for securing the extremities of the strip to said cover for holdingthe indicating device ina predetermined position against said flanges, said last mentioned means including means for longitudinally adjusting the strip and indicating device with respect to -said opening.

20.1n a thermostatic device, a cover, an indicating thermometer, an opening in said'cover and means for securing the thermometer to the inside of the coverso as to be visible fromy the outside including an elongated strip engaging the thermometer, a lug carried bythe cover to vbe engagedby one end of the strip to secure that end of the strip to the cover, and a'fastening means for securingvthe other end of the strip to the cover and for holding the first mentioned end in lof bimetallic material bent transversely intothe form of an elongated U-shaped member, means mounting said member for movement with respect to said base, the U-shaped member being mounted diagonally with respect to the length of said base, and a cover for said base enclosing said member, said cover having openings therein to facilitate the circulation of air past said member.

22. In a device of the character described comprising in combination, a base member, an elongated thermostatic element bent transversely at a portion intermediate the ends thereof, first switch means carried by said base member, second switch means moved by one end of said thermostatic ,element for engagement with said first switch means uponchanges in temperature affecting the thermostatic element, an adjusting member rotatably mounted on said base including a cam, means for mounting the thermostatic element on said base formovement with respect to said cam and for resiliently biasing the thermostatic element to positi'on'the other end thereof as determined by said cam member, one of said base and adjusting members having a cut-away portion'Y and the other of said members being provided with a projection extending into the cut-away portion to limit the rotation of the adjusting member.

23. In combination, on said base, switch adjusting means comprising a cam member rotatably mounted in said base, a scale member rotatably mounted in said base, means for adjustably securing said scale member to said cam member for' rotation therewith, a

` fixedly mounted indicator located adjacent to means to lock the cam and scale members in any desired adjusted position.

24. In a device of the character described comprising in combination, a base, a thermostatic switch mounted on said base, a cover for said switch adapted to be supported by said base, said cover having an elongated opening in the face a basea switch mounted l ne un.

thereof, an indicating thermometer, an elongated strip, meansfor connecting said thermometer to said strip, and means tor mounting said strip to the inside of said cover so that said thermometer will be visible through the opening in said cover.

- 25. In a device oi the character described, com'- prising in combination, switch means, a thermostat responsive primarily to variations in temperature of the surrounding atmosphere for actuating Y, said switch means, an electric heater controlled by said switch means, said thermostat being operative to automatically energize and deenergize said heater, and means comprising a predetermined mass of heat labsorbent material Which-mustrst be heated by said heater before the heat is tratted to raise the temperature of said thermostat above that of the surrounding atmosphere a predetermined time after energization of said heater.

26.- In a temperature responsive switch, a base, Y a thermostat on said base, a switch actuated by for said thermostat and said thermostat, a cover switch, anfopening in said cover, a thermometer within said cover and ing, means on said visible through said opencover for supporting said thermometer within said cover inaI position that is adjustable with respect to said opening, and in suche, position as to be visible through said open- A 27. In a device of the character described comprising in combination, a base, a thermostat mounted on said base, a Switch actuated by said thermostat, adjusting means for-said thermostat comprisinga cam rotatably mounted in said base,

a graduated dial' connected to said cam so that the latter may be rotated by the former, an arcuate slot in saiddiai, and a resilient member for f resisting rotation of the dial, said resilient member having an arm which extends through said arcuate slot.

28. in a device oi the character described comv .for cooperation with the graduations on said dial,

said arm also limiting the manual rotation of said dial by engagement with the ends of the slot.

29. In a' device of the character described coinprising in combination, a base, a thermostat mounted on said base, a switch actuated by said thermostat, adjusting means for said thermostat Vcomprising a cam rotatably mounted in saidbase,

a graduated dial connected to said cam so that the latter may be rotated by the former, an arcuate slot in said dial, a resilient member-'rior resisting rotation of the dial, said resilient member having an arm which extends through said arcuate slot, and a cover for said thermostat and switch, said cover tting over said base, and a slot in the top ci said cover through which said dial and pointer extend when said cover is in place over said base. J

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